Avoid character to byte conversions in motion subroutines.

* indent.h (compute_motion, vmotion): Add byte position argument.
* indent.c (compute_motion): Use it and avoid CHAR_TO_BYTE.
Add eassert.
(Fcompute_motion): Break long line.  Adjust call to compute_motion.
Use list5 for return value.
(vmotion): Use byte position argument and avoid call to CHAR_TO_BYTE.
Adjust comments, style and calls to compute_motion.
(Fvertical_motion): Adjust call to vmotion.
* window.c (Fdelete_other_windows_internal): Record window start
byte position and adjust call to vmotion.
(window_scroll_line_based): Likewise with call to compute_motion.
Use SET_PT_BOTH.
(Frecenter): Adjust calls to vmotion.

4 files changed, 66 insertions, 61 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index eee20d998dd..bc106df0cb2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,22 @@
 2013-03-07  Dmitry Antipov  <dmantipov@yandex.ru>
 
+        Avoid character to byte conversions in motion subroutines.
+        * indent.h (compute_motion, vmotion): Add byte position argument.
+        * indent.c (compute_motion): Use it and avoid CHAR_TO_BYTE.
+        Add eassert.
+        (Fcompute_motion): Break long line.  Adjust call to compute_motion.
+        Use list5 for return value.
+        (vmotion): Use byte position argument and avoid call to CHAR_TO_BYTE.
+        Adjust comments, style and calls to compute_motion.
+        (Fvertical_motion): Adjust call to vmotion.
+        * window.c (Fdelete_other_windows_internal): Record window start
+        byte position and adjust call to vmotion.
+        (window_scroll_line_based): Likewise with call to compute_motion.
+        Use SET_PT_BOTH.
+        (Frecenter): Adjust calls to vmotion.
+
+2013-03-07  Dmitry Antipov  <dmantipov@yandex.ru>
+
         * lisp.h (list2i, list3i): New functions.
         (list4i): Move from window.c and make LISP_INLINE.
         * editfns.c (make_lisp_time):
diff --git a/src/indent.c b/src/indent.c
index abb4e08ad08..fd692f0b149 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -1102,8 +1102,8 @@ static struct position val_compute_motion;
    the scroll bars if they are turned on.  */
 
 struct position *
-compute_motion (ptrdiff_t from, EMACS_INT fromvpos, EMACS_INT fromhpos,
-                bool did_motion, ptrdiff_t to,
+compute_motion (ptrdiff_t from, ptrdiff_t frombyte, EMACS_INT fromvpos,
+                EMACS_INT fromhpos, bool did_motion, ptrdiff_t to,
                 EMACS_INT tovpos, EMACS_INT tohpos, EMACS_INT width,
                 ptrdiff_t hscroll, int tab_offset, struct window *win)
 {
@@ -1186,8 +1186,11 @@ compute_motion (ptrdiff_t from, EMACS_INT fromvpos, EMACS_INT fromhpos,
   immediate_quit = 1;
   QUIT;
 
+  /* It's just impossible to be too paranoid here.  */
+  eassert (from == BYTE_TO_CHAR (frombyte) && frombyte == CHAR_TO_BYTE (from));
+
   pos = prev_pos = from;
-  pos_byte = prev_pos_byte = CHAR_TO_BYTE (from);
+  pos_byte = prev_pos_byte = frombyte;
   contin_hpos = 0;
   prev_tab_offset = tab_offset;
   memset (&cmp_it, 0, sizeof cmp_it);
@@ -1724,7 +1727,8 @@ of a certain window, pass the window's starting location as FROM
 and the window's upper-left coordinates as FROMPOS.
 Pass the buffer's (point-max) as TO, to limit the scan to the end of the
 visible section of the buffer, and pass LINE and COL as TOPOS.  */)
-  (Lisp_Object from, Lisp_Object frompos, Lisp_Object to, Lisp_Object topos, Lisp_Object width, Lisp_Object offsets, Lisp_Object window)
+  (Lisp_Object from, Lisp_Object frompos, Lisp_Object to, Lisp_Object topos,
+   Lisp_Object width, Lisp_Object offsets, Lisp_Object window)
 {
   struct window *w;
   Lisp_Object bufpos, hpos, vpos, prevhpos;
@@ -1767,7 +1771,8 @@ visible section of the buffer, and pass LINE and COL as TOPOS.  */)
   if (XINT (to) < BEGV || XINT (to) > ZV)
     args_out_of_range_3 (to, make_number (BEGV), make_number (ZV));
 
-  pos = compute_motion (XINT (from), XINT (XCDR (frompos)),
+  pos = compute_motion (XINT (from), CHAR_TO_BYTE (XINT (from)),
+                        XINT (XCDR (frompos)),
                         XINT (XCAR (frompos)), 0,
                         XINT (to),
                         (NILP (topos)
@@ -1789,28 +1794,23 @@ visible section of the buffer, and pass LINE and COL as TOPOS.  */)
   XSETINT (vpos, pos->vpos);
   XSETINT (prevhpos, pos->prevhpos);
 
-  return Fcons (bufpos,
-                Fcons (hpos,
-                       Fcons (vpos,
-                              Fcons (prevhpos,
-                                     Fcons (pos->contin ? Qt : Qnil, Qnil)))));
-
+  return list5 (bufpos, hpos, vpos, prevhpos, pos->contin ? Qt : Qnil);
 }
-
-/* Fvertical_motion and vmotion */
+
+/* Fvertical_motion and vmotion.  */
 
 static struct position val_vmotion;
 
 struct position *
-vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
+vmotion (register ptrdiff_t from, register ptrdiff_t from_byte,
+         register EMACS_INT vtarget, struct window *w)
 {
   ptrdiff_t hscroll = w->hscroll;
   struct position pos;
-  /* vpos is cumulative vertical position, changed as from is changed */
+  /* VPOS is cumulative vertical position, changed as from is changed.  */
   register EMACS_INT vpos = 0;
   ptrdiff_t prevline;
   register ptrdiff_t first;
-  ptrdiff_t from_byte;
   ptrdiff_t lmargin = hscroll > 0 ? 1 - hscroll : 0;
   ptrdiff_t selective
     = (INTEGERP (BVAR (current_buffer, selective_display))
@@ -1854,29 +1854,24 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
                                                        text_prop_object),
                          TEXT_PROP_MEANS_INVISIBLE (propval))))
             prevline = find_newline_no_quit (prevline - 1, -1, &bytepos);
-          pos = *compute_motion (prevline, 0,
-                                 lmargin,
-                                 0,
-                                 from,
+          pos = *compute_motion (prevline, bytepos, 0, lmargin, 0, from,
                                  /* Don't care for VPOS...  */
                                  1 << (BITS_PER_SHORT - 1),
                                  /* ... nor HPOS.  */
                                  1 << (BITS_PER_SHORT - 1),
-                                 -1, hscroll,
-                                 0,
-                                 w);
+                                 -1, hscroll, 0, w);
           vpos -= pos.vpos;
           first = 0;
           from = prevline;
+          from_byte = bytepos;
         }
 
-      /* If we made exactly the desired vertical distance,
-         or if we hit beginning of buffer,
-         return point found */
+      /* If we made exactly the desired vertical distance, or
+         if we hit beginning of buffer, return point found.  */
       if (vpos >= vtarget)
         {
           val_vmotion.bufpos = from;
-          val_vmotion.bytepos = CHAR_TO_BYTE (from);
+          val_vmotion.bytepos = from_byte;
           val_vmotion.vpos = vpos;
           val_vmotion.hpos = lmargin;
           val_vmotion.contin = 0;
@@ -1884,11 +1879,12 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
           return &val_vmotion;
         }
 
-      /* Otherwise find the correct spot by moving down */
+      /* Otherwise find the correct spot by moving down.  */
     }
-  /* Moving downward is simple, but must calculate from beg of line
-     to determine hpos of starting point */
-  from_byte = CHAR_TO_BYTE (from);
+
+  /* Moving downward is simple, but must calculate from
+     beg of line to determine hpos of starting point.  */
+
   if (from > BEGV && FETCH_BYTE (from_byte - 1) != '\n')
     {
       ptrdiff_t bytepos;
@@ -1905,17 +1901,12 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
                                                    text_prop_object),
                      TEXT_PROP_MEANS_INVISIBLE (propval))))
         prevline = find_newline_no_quit (prevline - 1, -1, &bytepos);
-      pos = *compute_motion (prevline, 0,
-                             lmargin,
-                             0,
-                             from,
+      pos = *compute_motion (prevline, bytepos, 0, lmargin, 0, from,
                              /* Don't care for VPOS...  */
                              1 << (BITS_PER_SHORT - 1),
                              /* ... nor HPOS.  */
                              1 << (BITS_PER_SHORT - 1),
-                             -1, hscroll,
-                             0,
-                             w);
+                             -1, hscroll, 0, w);
       did_motion = 1;
     }
   else
@@ -1924,11 +1915,9 @@ vmotion (register ptrdiff_t from, register EMACS_INT vtarget, struct window *w)
       pos.vpos = 0;
       did_motion = 0;
     }
-  return compute_motion (from, vpos, pos.hpos, did_motion,
+  return compute_motion (from, from_byte, vpos, pos.hpos, did_motion,
                          ZV, vtarget, - (1 << (BITS_PER_SHORT - 1)),
-                         -1, hscroll,
-                         0,
-                         w);
+                         -1, hscroll, 0, w);
 }
 
 DEFUN ("vertical-motion", Fvertical_motion, Svertical_motion, 1, 2, 0,
@@ -1995,7 +1984,7 @@ whether or not it is currently displayed in some window.  */)
   if (noninteractive)
     {
       struct position pos;
-      pos = *vmotion (PT, XINT (lines), w);
+      pos = *vmotion (PT, PT_BYTE, XINT (lines), w);
       SET_PT_BOTH (pos.bufpos, pos.bytepos);
     }
   else
diff --git a/src/indent.h b/src/indent.h
index acfd952754e..4eb3fed6a11 100644
--- a/src/indent.h
+++ b/src/indent.h
@@ -26,14 +26,14 @@ struct position
     int contin;
   };
 
-struct position *compute_motion (ptrdiff_t from, EMACS_INT fromvpos,
-                                 EMACS_INT fromhpos, bool did_motion,
-                                 ptrdiff_t to, EMACS_INT tovpos,
-                                 EMACS_INT tohpos,
+struct position *compute_motion (ptrdiff_t from, ptrdiff_t frombyte,
+                                 EMACS_INT fromvpos, EMACS_INT fromhpos,
+                                 bool did_motion, ptrdiff_t to,
+                                 EMACS_INT tovpos, EMACS_INT tohpos,
                                  EMACS_INT width, ptrdiff_t hscroll,
                                  int tab_offset, struct window *);
-struct position *vmotion (ptrdiff_t from, EMACS_INT vtarget,
-                          struct window *);
+struct position *vmotion (ptrdiff_t from, ptrdiff_t from_byte,
+                          EMACS_INT vtarget, struct window *);
 ptrdiff_t skip_invisible (ptrdiff_t pos, ptrdiff_t *next_boundary_p,
                           ptrdiff_t to, Lisp_Object window);
 
diff --git a/src/window.c b/src/window.c
index ed0c1283abe..77696131512 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2743,7 +2743,7 @@ window-start value is reasonable when this function is called.  */)
   struct window *w, *r, *s;
   struct frame *f;
   Lisp_Object sibling, pwindow, swindow IF_LINT (= Qnil), delta;
-  ptrdiff_t startpos IF_LINT (= 0);
+  ptrdiff_t startpos IF_LINT (= 0), startbyte IF_LINT (= 0);
   int top IF_LINT (= 0), new_top, resize_failed;
 
   w = decode_valid_window (window);
@@ -2782,6 +2782,7 @@ window-start value is reasonable when this function is called.  */)
   if (!NILP (w->buffer))
     {
       startpos = marker_position (w->start);
+      startbyte = marker_byte_position (w->start);
       top = WINDOW_TOP_EDGE_LINE (w)
         - FRAME_TOP_MARGIN (XFRAME (WINDOW_FRAME (w)));
       /* Make sure WINDOW is the frame's selected window.  */
@@ -2951,7 +2952,7 @@ window-start value is reasonable when this function is called.  */)
           Fset_buffer (w->buffer);
           /* This computation used to temporarily move point, but that
              can have unwanted side effects due to text properties.  */
-          pos = *vmotion (startpos, -top, w);
+          pos = *vmotion (startpos, startbyte, -top, w);
 
           set_marker_both (w->start, w->buffer, pos.bufpos, pos.bytepos);
           w->window_end_valid = 0;
@@ -4748,7 +4749,8 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
   register Lisp_Object tem;
   int lose;
   Lisp_Object bolp;
-  ptrdiff_t startpos;
+  ptrdiff_t startpos = marker_position (w->start);
+  ptrdiff_t startbyte = marker_byte_position (w->start);
   Lisp_Object original_pos = Qnil;
 
   /* If scrolling screen-fulls, compute the number of lines to
@@ -4756,8 +4758,6 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
   if (whole)
     n *= max (1, ht - next_screen_context_lines);
 
-  startpos = marker_position (w->start);
-
   if (!NILP (Vscroll_preserve_screen_position))
     {
       if (window_scroll_preserve_vpos <= 0
@@ -4765,10 +4765,8 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
           || NILP (Fget (KVAR (current_kboard, Vlast_command), Qscroll_command)))
         {
           struct position posit
-            = *compute_motion (startpos, 0, 0, 0,
-                               PT, ht, 0,
-                               -1, w->hscroll,
-                               0, w);
+            = *compute_motion (startpos, startbyte, 0, 0, 0,
+                               PT, ht, 0, -1, w->hscroll, 0, w);
           window_scroll_preserve_vpos = posit.vpos;
           window_scroll_preserve_hpos = posit.hpos + w->hscroll;
         }
@@ -4784,9 +4782,10 @@ window_scroll_line_based (Lisp_Object window, int n, int whole, int noerror)
     {
       Fvertical_motion (make_number (- (ht / 2)), window);
       startpos = PT;
+      startbyte = PT_BYTE;
     }
 
-  SET_PT (startpos);
+  SET_PT_BOTH (startpos, startbyte);
   lose = n < 0 && PT == BEGV;
   Fvertical_motion (make_number (n), window);
   pos = PT;
@@ -5321,7 +5320,7 @@ and redisplay normally--don't erase and redraw the frame.  */)
 
           iarg = max (iarg, this_scroll_margin);
 
-          pos = *vmotion (PT, -iarg, w);
+          pos = *vmotion (PT, PT_BYTE, -iarg, w);
           charpos = pos.bufpos;
           bytepos = pos.bytepos;
         }
@@ -5340,7 +5339,7 @@ and redisplay normally--don't erase and redraw the frame.  */)
       iarg = clip_to_bounds (this_scroll_margin, iarg,
                              ht - this_scroll_margin - 1);
 
-      pos = *vmotion (PT, - iarg, w);
+      pos = *vmotion (PT, PT_BYTE, - iarg, w);
       charpos = pos.bufpos;
       bytepos = pos.bytepos;
     }